Gerson Goldhaber, a UC Berkeley physicist who played a key role in identifying some of the fundamental particles of nature, then switched careers and helped show that the universe is expanding rather than contracting, died of natural causes at his home in Berkeley on July 19. He was 86.

Goldhaber "was a great physicist and a wonderful human being," said George Trilling, a professor emeritus at UC Berkeley who worked with him. "The number of observations that he was responsible for was remarkable."

He "had an unerring sense of where great discoveries were to be made, from the antiproton to the psi and charm particles, and finally to dark energy," longtime colleague Robert Cahn of the Lawrence Berkeley National Laboratory said in a statement. He had "a special talent for turning abstractions into something for which he could have an intuitive sense," said Cahn, who co-wrote with Goldhaber "The Experimental Foundations of Particle Physics."

As a part of a team led by Emilio Segre and Owen Chamberlain at the Lawrence Berkeley lab, Goldhaber played a key role in the discovery of the antiproton, the nuclear particle with the same mass as the proton but the opposite charge. Antimatter versions of all the other particles had been observed, but the antiproton remained elusive and some researchers doubted its existence. Even Goldhaber's brother Maurice, also a physicist, bet a colleague $500 that it would not be found.

Goldhaber and his then-wife, nuclear chemist/physicist Sulamith Low Goldhaber, developed a photographic emulsion detector that played a key role in the 1955 discovery of the particle. Segre and Chamberlain received the 1959 Nobel Prize in Physics for the feat. Some experts said they finally accepted the existence of the particle because Maurice paid up after losing the bet.

In 1960, the Goldhabers and Trilling formed the Trilling-Goldhaber experimental group, which three years later discovered the A meson, named after Goldhaber's son Amos. The A meson is one of a family of 30 elementary particles composed of a quark and an antiquark. Goldhaber later made a habit of naming newly discovered supernovas after the loved ones and children of colleagues.

In 1972, the Trilling-Goldhaber group began collaborating with physicist Burton Richter at the Stanford Linear Accelerator Center to search for new quarks. With Goldhaber doing the bulk of the data analysis, the team in 1974 announced the discovery of a particle composed of the previously unknown charm quark and charm antiquark. Goldhaber proposed that it be called a psi particle because its track resembled the Greek letter.

Almost simultaneously, a group at the Brookhaven National Laboratory led by MIT physicist Samuel Ting announced the discovery of the same particle, which they called the J particle. Richter and Ting won the1976 Nobel Prize in Physics for the discovery.

In 1989, Goldhaber changed gears and joined the Berkeley lab's Deep Supernova Search, which was looking for Type Ia supernovae. Those supernovae are called "standard candles" because each emits the same amount of light. By measuring how much light is lost in transit to the Earth, astronomers are able to calculate their distance from us, thereby using them as a measuring stick for the universe.

At the time, cosmologists thought the expansion of the universe caused by the Big Bang was slowing. Many presumed it would eventually begin collapsing back on itself, ending up in a reverse of the Big Bang sometimes called the "big crunch."

By analyzing data from 38 of the Type Ia supernovae, however, Goldhaber was able to report to his colleagues in 1997 that the expansion of the universe was actually accelerating. That was the earliest evidence for what came to be known, a year later, as "dark energy," a still mysterious force that is blowing the universe apart.

Gerson Goldhaber was born in Chemnitz, Germany, on Feb. 20, 1924, but moved with his family to Cairo in 1933 to escape Nazi persecution. He received his master's degree in physics from Hebrew University in Jerusalem in 1947 and his doctorate from the University of Wisconsin in 1950.

He became a naturalized United States citizen in 1953 while teaching at Columbia University. Later that year, he joined UC Berkeley's Radiation Laboratory, which is now known as the Lawrence Berkeley National Laboratory, and he spent the rest of his career there.

In 1965 on a family trip around the world, Goldhaber's wife fell into a coma in India and died. To console himself, Goldhaber took up art, eventually gravitating to painting and drawing. After he remarried in 1969 to poet and writer Judith Margoshes Golwyn, the couple collaborated on many art projects and books of poetry.